Input Impedance Characterization of a Single-Phase PFC in D-Q Frame

Small-signal stability analysis in a balanced three-phase system can be performed by extracting source and load impedance in a synchronous rotating frame (d-q) and using Generalized Nyquist Criterion (GNC). For a single-phase system or three-phase unbalance systems, like a data center power system, the derivation of input impedance and stability analysis in the d-q frame is not straightforward because of the system’s inherent time-variant condition due to the single-phase and unbalanced load. Existing approaches to analyze the stability of such a system are based on harmonics linearization in the stationary frame or by creating virtual frames and transforming the constructed three-phase system to another rotating frame. Inspired by the latter method, this paper models and characterizes the input impedance of a single-phase totem-pole power-factor-correction (PFC) converter in d-q frame based on virtual frames method, which is a vital step towards stability analysis of data power systems. This paper also analyzes the different control loops’ impact on the shaping of the PFC d-q impedance, which can provide insights for design-oriented stability analysis. The derived impedance model is verified with experimental measurement.